The present invention, in some embodiments thereof, relates to therapy, and more particularly, but not exclusively, to treatment of diseases and disorders of the respiratory tract using nitroxide radicals.
Oxidative stress is one of the key components of inflammatory disorders. In particular, it has been widely reported to play a role in airway inflammation in various forms of asthma [Henricks & Nijkamp, Pulm Pharmacol Ther 2001, 14:409-420; Li et al., Clin Immunol 2003, 109 250-265; Riedl & Nel, Curr Opin Allergy Clin Immunol 2008, 8:49-56]. The reported association between oxidative stress and airway inflammation is reflected by production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) [Andreadis et al., Free Radic Biol Med 2003, 35:213-225; Kharitonov & Barnes, Curr Allergy Asthma Rep 2003, 3:121-129; Maniscalco et al., Inflamm Res 2007, 56:58-69] and by an inverse correlation between endogenous levels of antioxidants and airway inflammatory processes [Mohan & Das, Med Sci Res 1997, 25:307-309; Dworski, Thorax 2000, 55:S51-S53; Rubin et al., Am J Respir Crit Care Med 2004, 169:393-398; Sackesen et al., J Allergy Clin Immunol 2008, 122:78-85; Kelly et al., Lancet 1999, 354:482-483; Picado et al., Allergy 2001, 56:43-49; Allan et al., Clin Exp Allergy 2010, 40:370-380].
Several decades of thorough research of biologically-relevant ROS have provided quite comprehensive knowledge and understanding of their chemical nature, the reactions of their formation and decay, the roles they play under physiological and pathophysiological conditions, and the mechanisms underlying their activities. So far, despite the available epidemiological, animal, molecular and immunological data indicating the association between antioxidants and asthma, the exact nature of the relationships and the potential for their therapeutic intervention remain unclear [Allan et al., Clin Exp Allergy 2010, 40:370-380].
The situation is even more complicated in the case of RNS, where nitric oxide (NO), an endogenous mediator having bronchodilating activity, may exhibit opposing effects. Nitric oxide is present in exhaled air and is increased in patients with asthma [Maniscalco et al., Inflamm Res 2007, 56:58-69; Massaro & Drazen, Immunol Allerg Clin North Am 1996, 16:735-751; Nevin & Broadley, Pharmacol Ther 2002, 95:259-293]. Persistently increased O2.− (an ROS) and NO in asthma lead to the formation of peroxynitrite (ONOO−), an RNS, and subsequent oxidation and nitration of essential cellular components, thus altering their function, and contributing to airway injury and inflammation [Andreadis et al., Free Radic Biol Med 2003, 35:213-225; Kharitonov & Barnes, Curr Allergy Asthma Rep 2003, 3:121-129]. On the other hand, inhalation of NO is used to treat newborns and critically ill asthmatic patients [Kinsella et al., Lancet 1992, 340:819-820; Kacmarek et al., Am J Respir Crit Care Med 1996, 153:128-135; Rishani et al., Pediatr Pulmonol 1999, 28:451-453; Gerlach et al., Am J Respir Crit Care Med 2003, 167:1008-1015]. The augmented availability of NO in the lungs may represent a plausible approach for the treatment of asthma; however, the mechanisms underlying the processes leading to the decreased expression of this molecule have not been fully elucidated [Nevin & Broadley, Pharmacol Ther 2002, 95:259-293; Lagente & Advenier, Curr Opin Investig Drugs 2004, 5:537-541; Antoniu, Curr Opin Investig Drugs 2010, 11:543-549].
Dietary supplementation of common antioxidants has been tested for several decades in an attempt to prevent or treat asthma and other airway inflammatory disorders [Locksley, Cell 2010, 140:777-783; Li et al., Clin Immunol 2003, 109 250-265; Andreadis et al., Free Radic Biol Med 2003, 35:213-225; Picado et al., Allergy 2001, 56:43-49; McNally, J Ir Med Assoc 1953, 33:175-178; Braskett & Riedl, Curr Opin Allergy Clin Immunol 2010, 10:34-41; Fogarty et al., Clin Exp Allergy 2003, 33:1355-1359; Greene, Nutrition 1999, 15:899-907; Kelly, Proc Nutr Soc 2005, 64:510-526]. However, the reported efficacy of antioxidant therapy is still equivocal [Misso & Thompson, Redox Rep 2005, 10:247-255; Murr et al., Med Hypotheses 2005, 64:973-977] and in many cases disappointing [Allan et al., Clin Exp Allergy 2010, 40:370-380; Dunstan et al., Clin Exp Allergy 2007, 37:180-187; Greene, J Am Coll Nutr 1995, 14:317-324; Hernandez et al., Inhal Toxicol 2009, 21:173-181].
Cyclic nitroxides are relatively stable free radicals which can undergo one-electron redox reactions to form the respective hydroxylamine and/or oxoammonium compounds, as depicted in Scheme 1 below for 2,2,6,6-tetramethyl-piperidine-N-oxyl (Tempo), a commonly used nitroxide:

Cyclic hydroxylamines have very weak O—H bonds, so cyclic nitroxides rarely participate in hydrogen abstraction reactions. However, being radicals, the nitroxides react rapidly with other radicals including HO2. [Goldstein et al., J Am Chem Soc 2003, 125:789-795; Goldstein et al., J Phys Chem A 2006, 110:3679-3685], carbon-centered radicals [Asmus et al., Int J Radiat Biol Relat Stud Phys Chem Med 1976, 29:211-219; Beckwith et al., J Am Chem Soc 1992, 114:983-4992; Bowry & Ingold, J Am Chem Soc 1992, 114:4992-4996], peroxyl radicals [Goldstein & Samuni, J Phys Chem A 2007, 111:1066-1072], thiyl radicals [Goldstein et al., J Phys Chem A 2008, 112:8600-8605], .OH [Samuni et al., J Am Chem Soc 2002, 124:8719-8724], .NO2 [Goldstein et al., J Am Chem Soc 2003, 125:8364-8370] and CO3.− [Goldstein et al., Chem Res Toxicol 2004, 17:250-257] without giving rise to secondary radicals. In addition, nitroxide radicals inhibit free radical formation via the Fenton reaction by oxidizing reduced metal ions such as CuI or FeII [Samuni et al., Biochemistry 1991, 30:555-561; Bar-On et al., J Am Chem Soc 1999, 121:8070-8073].
Nitroxides have been reported to exhibit anti-inflammatory, radioprotective, anti-mutagenic, anti-hypertensive, and anticancer activities, with Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) being a particularly widely studied nitroxide [Soule et al., Free Radic Biol Med 2007, 42:1632-1650; Soule et al., Antioxid Redox Signal 2007, 9:1731-1743].
Nitroxides have been reported to protect experimental animals against hyperoxia-induced brain damage [Howard et al., J Neurochem 1996, 67:2045-2050], experimental pancreatitis [Sledzinski et al., Int J Pancreatol 1995, 18:153-160], closed head injury induced by mechanical trauma [Beit-Yannai et al., Brain Res 1996, 717:22-28], and injuries associated with excessive NO production such as those resulting from multiple organ failure, transient cerebral ischemia, carrageenan-induced pleurisy, and dinitrobenzenesulfonic acid-induced colitis [Wilcox & Pearlman, Pharmacol Rev 2008, 60:418-469; Wilcox, Pharmacol Ther 2010, 126:119-145].
Nitroxides have also been reported to attenuate oxidative damage in various models such as lipid peroxidation in liver microsomes [Miura et al., Arch Biochem Biophys 1993, 300:148-156; Antosiewicz et al., Free Radic Biol Med 1997, 22:249-255; Cighetti et al., Chem Phys Lipids 1997, 88:97-106], tumor necrosis factor cytotoxicity [Pogrebniak et al., J Surg Res 1991, 50:469-474], thymocyte apoptosis [Slater et al., Biochem J 1995, 306:771-778], and post-ischemic reperfusion injury [Beaulieu et al., J Cereb Blood Flow Metab 1998, 18:1022-1031; Zeltcer et al., Free Radic Biol Med 2002, 32:912-919; Zeltcer et al., Free Radic Res 1997, 27:627-635].
Krishna et al. [J Med Chem 1998, 41:3477-3492] reported that the protective effects of cyclic nitroxides against oxidative damage are not dependent on ring size, but are enhanced by basic side chains.
U.S. Pat. No. 6,605,619 describes oxazolidine-derived and piperidine-derived nitroxides and hydroxylamines, and uses thereof for treating or preventing conditions such as inflammation, cancer, diabetes, cardiovascular disorders, weight gain, polyps and/or chronic pain.
U.S. Patent Application Publication No. 2012/0263650 describes compounds comprising a non-steroidal anti-inflammatory drug moiety and a nitroxide-containing moiety such as a TEMPO moiety, as well as uses thereof in the treatment of conditions such as inflammation, cancer, diabetes, cardiovascular disorders, weight gain, asthma, polyps and/or chronic pain.
U.S. Patent Application Publication No. 2008/0139525 describes synergistic combinations of a superoxide dismutase mimetic such as manganese compound or nitroxides with a selenium compound, for treating inflammatory, autoimmune, vascular and cardiovascular conditions.
Additional background art includes Arieli et al. [Free Radic Res 2008, 42:114-123], Aronovitch et al. [Free Radic Biol Med 2007, 42:1317-1325], Barnes [Proc Am Thorac Soc 2004, 1:264-268], Beers & Morrisey [J Clin Invest 2011, 121:2065-2073], Bergeron et al. [Can Respir J 2010, 17:e85-e93], Cho et al. [J Allergy Clin Immunol 2004, 114:429-435], Exo et al. [J Neurotrauma 2009, 26:2403-2408], Jubeh et al. [J Drug Target 2006, 14:155-163], Kirkham & Rahman [Pharmacol Therapeut 2006, 111:476-494], Komarov et al. [Biochem Biophys Res Commun 1994, 201:1035-1042], Krishna et al. [PNAS USA 1992, 89:5537-5541], Krishna et al. [J Biol Chem 1996, 271:26018-26025], Iannonea et al. [Biochem Biophys Acta 1989, 991:90-96], Mabalirajan et al. [J Appl Physiol 2009, 107:1285-1292], Mitchell et al. [Biochemistry 1990 29:2802-2807], Offer & Samuni [Free Radic Biol Med 2002, 32:872-881], Postma & Timens [Proc Am Thorac Soc 2006, 3:434-439], Reddan et al. [Exp. Eye Res 1993, 56:543-554], Samuni & Barenholz [Free Radic Biol Med 1997, 22:1165-1174], Samuni & Barenholz [Free Radic Biol Med 2003, 34:177-185], Samuni et al. [Biochemistry 1991, 30:555-561], Samuni et al. [J Biol Chem 1998, 263:17921-17924], Swartz et al. [Biochem Biophys Acta 1986, 888:82-90], Takeshita et al. [Biochem Biophys Res Commun 1991, 177:874-880], Utsumi et al. [Biochem Biophys Res Commun 1990, 172:1342-1348], Wagner et al. [Clin Exp Allergy 2008, 38:501-511], Wasserman et al. [Langmuir 2007, 23:1937-1947] and Zuoa et al. [Mol Immunol 2013, 56:57-63].